Negative pressure wound therapy (NPWT) has become widely used as a treatment mechanism for chronic or acute wounds. The therapy utilises the application of negative pressure to a wound. This causes mechanical contraction of the wound and/or micro-deformation of the wound-bed stimulating increased blood flow in the surrounding tissues and formation of new granulation tissue. Fluid and other deleterious material is removed from the wound. The wound site is also protected from external contaminants. Often the negative pressure is transmitted to and fluid removed from the wound-bed via a porous wound filler.
Known wound fillers are composed of either foam or gauze and both of these options work well in transmitting negative pressure and removing fluid.
Typically foam fillers, which tend to be of an open celled and possibly reticulated nature, are cut to shape and then packed into the wound cavity. Alternatively, if gauze is used then a pad of gauze is formed and then packed into the cavity. The wound and filler is then sealed using a drape and negative pressure applied via tubes connected in some way through the drape to a source of negative pressure such as a vacuum pump. A single or multi-lumen tube can be utilised to connect the wound site to the negative pressure source. Optionally, the tube or tubes can be fixed to the wound site via a coupling, sometimes referred to as a suction head, adhered to the top of the drape. Alternatively, the tube or tubes can themselves be passed under the drape or through the drape.
US2008/0004549 discloses a system for applying negative pressure on a wound which includes a device configured to provide negative pressure, a dressing sealably covering the wound and a spray-in foam located within the wound below the dressing material. Use of the spray-in foam overcomes the problem that a process of applying a dressing is tedious and time consuming. Unfortunately, US2008/0004549 does not suggest any material which would be suitable as a spray-in foam. Neither does the disclosure teach how the spray-in foam could, in practice, be applied at a wound site. In this sense the patent application is silent as to the necessary details which would enable a skilled person to use spray-in foam as suggested.
The technique suggested in US2008/0004549 is also prone to a problem caused as the foam is sprayed into a wound site. That is to say the foam rises up uncontrollably and would tend to spread too far vertically as well as over the peri-wound area. As such, the foam would require removing from around the wound to prevent skin maceration. Cutting or trimming wound fillers presents a risk to the clinician of leaving behind wound filler in a patient. This could hinder healing and may cause a rejection reaction from the patient's body a future date.
By adhering the drape securely to the peri-wound area (the healthy skin/dermis surrounding the wound), injected foam is prevented or substantially prevented from making contact with the healthy skin/dermal surface. It is well known to those in the art that wound exudate should be prevented, or at least try to prevent as much as possible from making contact with healthy skin/dermis.
For wounds that occur on awkward areas of the body, the packing of the wound can be problematical regardless of the prior known filling technique which is utilised. For example, if the wound is on the side or underside of a body then the filler can easily fall out before a clinician has an opportunity to apply the drape over the filler. Alternatively, the patient may be required to adopt an uncomfortable position in order to prevent the filler from falling out of the wound site. Even the spray in foam technique suggested in US2008/0004549 is prone to such a problem.